No problem, let's work through this together. We're starting with 891678777 and are subtracting 812202028 from it.

Step 1: We'll start by subtracting the digit 8 and the borrow 0 from 7 in column 1 and get -1.
We add -1 to 10 and get 9 as the first digit of the result.

Step 2: We'll start by subtracting the digit 2 and the borrow 1 from 7 in column 2 and get 4.
4 is the next digit of our result.

Step 3: We'll start by subtracting the digit 0 and the borrow 0 from 7 in column 3 and get 7.
7 is the next digit of our result.

Step 4: We'll start by subtracting the digit 2 and the borrow 0 from 8 in column 4 and get 6.
6 is the next digit of our result.

Step 5: We'll start by subtracting the digit 0 and the borrow 0 from 7 in column 5 and get 7.
7 is the next digit of our result.

Step 6: We'll start by subtracting the digit 2 and the borrow 0 from 6 in column 6 and get 4.
4 is the next digit of our result.

Step 7: We'll start by subtracting the digit 2 and the borrow 0 from 1 in column 7 and get -1.
We add -1 to 10 and get 9 as the next digit of the result.

Step 8: We'll start by subtracting the digit 1 and the borrow 1 from 9 in column 8 and get 7.
7 is the next digit of our result.

Step 9: We'll start by subtracting the digit 8 and the borrow 0 from 8 in column 9 and get 0.
0 is the next digit of our result.

So, 891678777 - 812202028 = 79476749.